CO_2水合物导热特性的分子动力学模拟

使用分子动力学模拟方法在NVT系综下对结构完整CO_2水合物以及结构缺陷CO_2水合物进行了导热模拟计算.对于结构完整的CO_2水合物,在200-230 K温度区间内,体系导热系数由0.4684 W·m~(-1)·K~(-1)变化到0.4836 W·m~(-1)·K~(-1),温度相关性较弱;而在230-280 K温度区间内,体系导热系数由0.4836 W·m~(-1)·K~(-1)变化到0.7494 W·m~(-1)·K~(-1),温度相关性变强;另外,通过计算功率图谱发现主体分子对水合物体系的导热贡献更大.对于结构缺陷CO_2水合物,发现晶穴占有率和笼形结构缺陷对体系导热均有一定影响,空笼晶胞导热系数约为完整晶胞导热系数的86.67%,体系的导热能力主要取决于主体结构的性质.

Molecular dynamics simulation of thermal conductivity of CO2 hydrate

The CO2 hydrates with complete structure and CO2 hydrate with defect structure were simulated and calculated under NVT ensemble by using molecular dynamics simulations. For the CO2 hydrate with complete structure, the thermal conductivity of the system changes from 0.4684 Wm-1K-1 to 0.4836 Wm-1K-1 in the temperature range of 200-230 K, and the temperature dependence is weak; while in the temperature range of 230-280 K, the thermal conductivity of the system changes from 0.4836 Wm-1K-1 to 0.7494 Wm-1K-1, and the temperature dependence becomes stronger. In addition, it is found that the host molecules contribute more to the thermal conductivity of the hydrate system by calculating the power spectrum. For CO2 hydrate with defect structures, it is found that the crystal hole occupancy rate and the defect structures of cages have certain effects on the thermal conductivity of the system. The thermal conductivity of the empty cage cell is about 86.67% of the thermal conductivity of the complete cell. The thermal conductivity of the system depends mainly on the nature of the main structures.